The Constitutional Court's ruling holding the coalition guilty of voter fraud in last December's general election came after one of the protesters occupying Bangkok's domestic Don Muang airport died in a reported grenade blast, which also injured 22 others.

The protesters have occupied both Don Muang and the Suvarnabhumi international airport demanding the resignation of the government, saying Somchai is only heading a proxy government for his brother-in-law and former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 coup..

The court ruling ordered the People Power Party-led coalition dissolved which, under the 2007 constitution, would also require Somchai to leave office and ban the party and its coalition partners from politics for five years, the Thai News Agency reported.

An attorney for the PPP, however, said the party won't accept the ruling as the Constitutional Court gave no formal advance notice.

In the incident at Don Muang, the Bangkok Nation reported a grenade was fired into a terminal building, killing a 29-year-old protester and injuring 22 others, five of them seriously. Guards of the protesters told the Nation they saw the attacker speed off on a vehicle.

On Sunday, a blast from a grenade suspected of being tossed by counter-demonstrators at another location injured about 50 protesters.

Since the Sunday incident, the protesters have left the government compound after occupying it since August and are concentrating their effort at the two airports, the Bangkok Post reported.

The move also was seen as designed to facilitate Friday's royal ceremonies for the 81st birthday of Thailand's King Bhumibol Adulyadej.

Tens of thousands of passengers have been stranded across the country since the airport protests. On Monday, the protesters allowed 37 of the 88 planes parked at Suvarnabhumi to fly out empty to pick up stranded passengers at other airports.